The p53 gene is one of the most studied and well-known genes. p53 plays a key role in cellular stress response mechanisms by converting a variety of different stimuli, for example, DNA damage, deregulation of transcription or replication, and oncogene transformation, into cell growth arrest or apoptosis. However, loss of p53 activity in tumors is associated with faster tumor progression and resistance to cancer treatment. See, e.g., U.S. Pat. No. 6,593,353; see also U.S. Pat. Nos. 6,998,117; 6,017,524; 5,908,750; and 5,744,310.; M. Greenblatt et al., Cancer Res. 54, 4855-4878 (1994). Hence, there is a need for new ways to treat cancers in which p53 deficiency is found.